The present invention relates to a compatibilizing agent for improving the compatibility between different polymers which are poorly compatible with each other in a polymer blend, more particularly, in a polymer blend of a nonpolar polymer and a polar polymer.
It has been a general trend in the field of polymer science and technology to try to improve the mechanical properties, moldability and the like of a polymer by blending therewith a different polymer. As is well known in the field of polymer blends, various properties of the resulting polymer blend are influenced by the compatibility of a polymer to be blended.
The blend of different polymers include blends of nonpolar polymers, blends of a nonpolar polymer and a polar polymer and blends of polar polymers. In order to improve the solubility between the component polymers in the blend, various methods have heretofore been proposed.
For example, for blends of nonpolar polymers (e.g., blends of a polyolefin such as polyethylene and polystyrene), there are known a method in which styrene/butadiene/styrene block copolymer is used as a compatibilizing agent (see U.S. Pat. Nos. 4,386,187 and 4,386,188), a method in which ethylene/vinyl acetate copolymer is used as a compatibilizing agent (see Japanese Patent Laid-Open No. 43031/1973) and the like. These methods are effective to some extent in their own way.
Further, for blends of, for example, polar polymers, there is known a method in which compatibility is improved by blending a polymer having pendant cyclic iminoether groups and a polymer having groups coreactive with the cyclic iminoether groups (see U.S. Pat. No. 4,864,002). This method is effective so far as it is applied to incompatible polymers the polar groups of which are coreactive but is ineffective when it is applied to a blend of a polymer having cyclic iminoether groups and a nonpolar polymer. Further, in the case of blends of nonpolar polymers, the addition of a polymer having cyclic iminoether groups brings about no improvement in the compatibility.
Up to date, no polymer has been found which serves as a compatibilizing agent which can improve the compatibility between different polymers, particularly between a polar polymer and a nonpolar polymer, and accordingly the development of such a compatibilizing agent is strongly desired.